The invention relates generally to systems for extracting prosthetic components, and more particularly, to systems for extracting an implanted acetabular cup from the acetabulum of a patient.
Joint arthroplasty is a well known surgical procedure by which a diseased and/or damaged natural joint is replaced by a prosthetic joint. Joint arthroplasty is commonly performed for hips, knees, elbows, and other joints. The health and condition of the joint to be replaced dictate the type of prosthesis necessary to replace the natural joint. For example, in a total hip arthroplasty an acetabular cup is implanted in the acetabular cavity in the pelvis to replace the natural acetabulum. Replacement of the acetabulum is necessary when there is an inadequate articulation surface for a head or ball of a prosthetic femoral component.
To implant an acetabular cup, a cavity is reamed in the acetabulum. The reamed cavity generally conforms to an outer surface of the acetabular cup. The acetabular cup is then inserted into the formed cavity and secured by mechanical means, by interference fit, or by a combination thereof. The acetabular cup is positioned in the pelvis at a fixed orientation in the acetabulum so as to emulate the patient's natural anatomy. The implanted cup should remain stable to prevent erosion of the surrounding bone and to inhibit generation of excessive wear debris in the prosthetic joint.
Various methods and techniques have been used to secure an acetabular cup within a formed acetabular cavity. One such method includes the use of bone cement to secure the acetabular cup to the acetabulum. Another technique utilizes an acetabular cup having holes for receiving screws, or other types of fasteners, to affix the acetabular cup to bone. A further method includes the implantation of an acetabular cup having an outer surface with various surface features to enhance fixation of the cup within the acetabular cavity.
While the above-described techniques achieve varying levels of success in providing long term fixation of the acetabular cup, surgical revision of the implanted cup is often necessary after an extended period of time. However, removal of the acetabular cup, especially cups without engagable inner surface features, can be difficult. In one technique for removing acetabular cups without inner surface features, such as an inner lip, osteotomes are taken about the outer surface of the acetabular cup and brute force is applied to achieve removal of the cup. More particularly, an osteotome chisel (see FIG. 7) is used to chisel away material at the cup/bone or bone/cement interface until the cup can be forcibly removed from the acetabulum. However, the aggressive use of force can result in the loss and/or fracture of essential bone. This difficult and awkward procedure poses a significant obstacle to successful surgical revision of an acetabular cup.
It would, therefore, be desirable to provide a system for removing implanted acetabular cups, and particularly cups without inner surface features, which minimizes the need for osteotomes, as well as the amount of force required to remove the implanted cup.